One of the most interesting “what ifs” of the Second World War, Unternehmen Seelöwe, Hitler’s planned invasion of Britain, is generally regarded as doomed to failure.

Not so says independent historian Leander. Arguing that treatments of the war have overlooked many German sources, River Wide, Ocean Deep lays the evidence for a more serious consideration of Seelöwe. Leander opens with a chapter on the general strategic situation in Europe following the fall of France, which caused Hitler to consider Seelöwe. He then discusses the state of scholarship on this “what if.” In the chapters that follow, he explores, often in considerable some detail various aspects of the preparations.

One chapter deals with the German transport fleet, which appears perhaps not as ramshackled as usually described, and it is followed by a second discussing the respective small warships – torpedo boats, gun boats, and so forth – on both sides, which would have played a major role in effecting, and opposing, the crossing. German diversionary preparations get a chapter, as does their mining plans. Individual chapters follow on coast artillery, British naval aviation and maritime patrol capability, and U-boat operations. The main British defensive forces are dealt with in four chapters, on the Royal Navy, the British Army, Bomber Command, and Fighter Command. For the Germans, Leander gives us chapters on the airborne troops, Army units, the Kriegsmarine, and the Luftwaffe. The main text concludes with a chapter cleverly titled “The Jokers,” in which Leander addresses some “wild card” possibilities, such as the German equivalent of Coastal Command, which seems to have been omitted in most accounts of Seelöwe, the Italian air component, again, generally overlooked, and German Brandenburger special operations forces.

Leander includes several interesting appendices, notably one on German convoy planning, a 1942 British evaluation of the threat, and even one on the “Channel Dash” of February 1942, which arguably demonstrated weaknesses in Britain’s coastal security. River Wide, Ocean Deep does have several weaknesses. The chapters might havebeen arranged so that the narrative flowed more readily. In addition, the lack of notes and an index, present problems when trying to follow up on ideas.

Despite these problems, River Wide, Ocean Deep is a valuable critical analysis of the state of scholarship on Seelöwe, and worth a read by anyone interested in World War II.